This application claims the priority of German patent 197 06 383.7, filed Feb. 19, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a breathing device for a crankcase of an internal combustion engine.
The SAE (Society of Automotive Engineers) Paper (February 1992) "Cosworth MBA Engine", Poole et al., page 8, discloses a generic breathing device for a crankcase of an internal combustion engine, in which, for oil separation, the blow-by oil mixture from the crankcase is guided into a housing in which a balancing shaft is mounted. The balancing shaft comprises a tubular piece with orifices, which forms a separation space and which is arranged between two balancing weights. The rotating balancing shaft likewise sets in rotation the blow-by oil mixture which has flowed out of the crankcase into the housing of the balancing shaft, the oil droplets contained in the blow-by gases being for the most part thrown against the outer wall of the balancing shaft and running off from the housing of the latter into the oil sump of the internal combustion engine. The pure blow-by gases pass via the orifices of the tubular piece into the separation space of the balancing shaft and from there into an intake system of the internal combustion engine. A relatively small proportion of the oil droplets nevertheless passes, together with the blow-by gases, into the separation space of the balancing shaft, is thrown against the inner wall of the tubular piece and passes again, via the orifices of the tubular piece, into the housing surrounding the balancing shaft, although the blow-by gases flowing through the same orifices into the balancing shaft may entrain again the oil droplets which have just emerged. Furthermore, the tubular piece used as the separation space constitutes an additional outlay in terms of the construction of the breathing device.
Reference is also made to U.S. Pat. Nos. 5,542,402 and 5,261,380 for the general technical background.
The object of the invention is to design a breathing device in such a way that, for a low outlay in terms of construction, the oil separation degree of the device is improved.
This object is achieved, according to the invention, by providing a breathing device for a crankcase of an internal combustion engine, comprising: a cylinder head defining a cylinder head space communicating with the crankcase of the internal combustion engine; a balancing shaft rotatably arranged in said cylinder head space, said balancing shaft defining a gas-guiding space communicating with an intake system of the internal combustion engine; at least one mass-balancing weight disposed on said balancing shaft, said at least one mass-balancing weight defining at least one oil discharging radial bore communicating said gas-guiding space with said cylinder head space, said at least one mass-balancing weight defining at least one axial feed bore communicating said cylinder head space with said at least one oil discharging radial bore.
An essential advantage of the breathing devices according to the invention is the increase in the oil separation rate. The spatial separation of the orifices for feeding the blow-by oil mixture into the mass-balancing weights, of the radial bores for the subsequent discharge of the oil droplets separated in the mass-balancing weights and of the gas-guiding space for discharging the blow-by gas into the intake system of the internal combustion engine prevents oil droplets which have already been separated from being entrained into the intake system. Due to the centrifugal forces acting on the blow-by oil mixture by virtue of the rotating balancing shaft, air and oil are positively separated from one another in the mass-balancing weights, air and oil being transferred through different bores after separation. There is no need for any additional outlay in terms of components, since the breathing device can be integrated into the balancing shaft and the mass-balancing weights. The machining outlay is low, since it is necessary only to introduce bores in the balancing shaft and the mass-balancing weights. An additional separation space can be dispensed with. The centrifugal force acting on the oil is substantially higher than the gravitational force likewise acting on the oil, so that the oil-discharging radial bores can be arranged at any desired location on the circumference of the mass-balancing weights and any inclined position of the internal combustion engine or vehicle still has no influence on oil separation.
Dimensioning the outflow resistance by reducing the diameter in the end region of the oil-discharging radial bores makes it possible to ensure that only oil emerges from the radial bores, but not the air.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.